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Pseudorabies virus protein homologous to herpes simplex virus type 1 ICP18.5 is necessary for capsid maturation.

In pseudorabies virus (PrV), an open reading frame that partially overlaps the gene for the essential glycoprotein gII has been shown to encode a protein homologous to the ICP18.5 polypeptide of herpes simplex virus type 1 (N. Pederson and L. Enquist, Nucleic Acids Res. 17:3597, 1989). To study the function of this protein during the viral replicative cycle, a PrV mutant which carries a beta-galactosidase expression cassette interrupting the ICP18.5(PrV) gene was constructed. This mutant could be propagated only on cell lines that were able to provide ICP18.5(PrV) in trans after transformation with a corresponding genomic PrV DNA fragment. Detailed analysis showed that inactivation of the ICP18.5(PrV) gene did not impair infection of noncomplementing cells, nor did it impair early or late gene expression, as shown by immunoprecipitation of glycoproteins gII, gIII, and gp50. Surface localization of glycoproteins as demonstrated by fluorescence-activated cell sorting analyses was also not affected. Southern blot hybridizations, however, showed that cleavage of replicative concatemeric viral DNA did not occur in noncomplementing cells infected by the ICP18.5 mutant PrV. In addition, electron microscopic analysis revealed an accumulation of empty capsids in the nucleus of mutant-infected noncomplementing cells. We conclude that the ICP18.5(PrV) protein is necessary for viral replication and plays an essential role in the process of mature capsid formation.

Animals↗

Stability in controlling viral replication identifies long-term nonprogressors as a distinct subgroup among human immunodeficiency virus type 1-infected persons.

Long-term nonprogressors (LTNPs) of human immunodeficiency virus type 1 (HIV-1) infection are characterized by low levels of HIV-1 replication and viral load. However, it has not been established whether they differ in this regard from progressors from the very early stage of infection. By studying peripheral blood mononuclear cell (PBMC) specimens from a longitudinally monitored cohort of HIV-1-infected men, we found that HIV-1 proviral copy numbers and HIV-1 mRNA expression levels as low or lower than those seen in seven carefully selected LTNPs were commonly observed in specimens collected soon after seroconversion from 28 subjects who became infected while under observation. However, only the LTNPs were able to stably maintain such an efficient viral control over time. Because of the instability of the early control of HIV-1 replication, the predictive value of HIV-1 mRNA expression in PBMCs at postseroconversion was found to be limited but significantly increased during the first year of infection. Besides their diagnostic implications, these data support the idea that LTNPs may be a pathophysiologically distinct subgroup among persons infected with HIV-1.

Cohort Studies↗

U20, a novel small nucleolar RNA, is encoded in an intron of the nucleolin gene in mammals.

We have found that intron 11 of the nucleolin gene in humans and rodents encodes a previously unidentified small nucleolar RNA, termed U20. The single-copy U20 sequence is located on the same DNA strand as the nucleolin mRNA. U20 RNA, which does not possess a trimethyl cap, appears to result from intronic RNA processing and not from transcription of an independent gene. In mammals, U20 RNA is an 80-nucleotide-long, metabolically stable species, present at about 7 x 10(3) molecules per exponentially growing HeLa cell. It has a nucleolar localization, as indicated by fluorescence microscopy following in situ hybridization with digoxigenin-labeled oligonucleotides. U20 RNA contains the box C and box D sequence motifs, hallmarks of most small nucleolar RNAs reported to date, and is immunoprecipitated by antifibrillarin antibodies. It also exhibits a 5'-3' terminal stem bracketing the box C-box D motifs like U14, U15, U16, or Y RNA. A U20 homolog of similar size has been detected in all vertebrate classes by Northern (RNA) hybridization with mammalian oligonucleotide probes. U20 RNA contains an extended region (21 nucleotides) of perfect complementarity with a phylogenetically conserved sequence in 18S rRNA. This complementarity is strongly preserved among distant vertebrates, suggesting that U20 RNA may be involved in the formation of the small ribosomal subunit like nucleolin, the product of its host gene.

Base Sequence↗

Calspermin gene transcription is regulated by two cyclic AMP response elements contained in an alternative promoter in the calmodulin kinase IV gene.

The transcript for the high-affinity Ca2+/calmodulin-binding protein calspermin is generated from the gene encoding Ca2+/calmodulin-dependent protein kinase IV only in postmeiotic germ cells during spermatogenesis. We demonstrate that this testis-specific calspermin transcript can be produced in heterologous cells by utilization of a promoter located in an intron of the calmodulin (CaM) kinase IV gene. Critical motifs within this promoter are two cyclic AMP response element (CRE)-like sequences located about -70 and -50 bp upstream of the transcriptional initiation site. Both CRE motifs are footprinted by the authentic testis-specific transcriptional activator CREM tau or by CREM tau present in adult testis nuclear extract. Whereas a 2.1-kb DNA fragment containing the calspermin promoter is inactive when transfected into NIH 3T3 cells, activity can be restored by cotransfection of CREM tau and protein kinase A or CaM kinase IV but not CaM kinase II alpha. Restoration of activity is greatly reduced by mutation of the two CRE motifs. Since CRE-like motifs have been identified in many genes uniquely expressed in postmeiotic germ cells, which contain abundant CREM tau protein, we suggest that CREM tau may function as one transcription factor responsible for the expression of postmeiotic germ cell-specific genes.

3T3 Cells↗

Repressive effect of Sp1 on the C/EBPalpha gene promoter: role in adipocyte differentiation.

Expression of C/EBPalpha is required for differentiation of 3T3-L1 preadipocytes into adipocytes. Previous investigations indicated that transcription of the C/EBPalpha gene is sequentially activated during differentiation, initially by C/EBPbeta and C/EBPdelta and later by C/EBPalpha (autoactivation). These events are mediated by a C/EBP regulatory element in the promoter of the C/EBPalpha gene. This article presents evidence that members of the Sp family, notably Sp1, act repressively on the C/EBPalpha promoter prior to the induction of differentiation. Sp1 was shown to bind to a GC box at the 5' end of the C/EBP regulatory element in the C/EBPalpha promoter and, in so doing, to competitively prevent binding to and transactivation of the promoter by the C/EBPs. One of the differentiation inducers methylisobutylxanthine (a cAMP phosphodiesterase inhibitor) or Forskolin, both of which increase the cellular cAMP level, causes down-regulation of Sp1. This decrease in Sp1 level early in the differentiation program appears to facilitate access of C/EBPbeta and/or C/EBPdelta to the C/EBP regulatory element and, thereby, derepression of the C/EBPalpha gene.

3T3 Cells↗

Both binding and activation of p38 mitogen-activated protein kinase (MAPK) play essential roles in regulation of the nucleocytoplasmic distribution of MAPK-activated protein kinase 5 by cellular stress.

The p38 mitogen-activated protein kinase (MAPK) pathway is an important mediator of cellular responses to environmental stress. Targets of p38 include transcription factors, components of the translational machinery, and downstream serine/threonine kinases, including MAPK-activated protein kinase 5 (MK5). Here we have used enhanced green fluorescent protein fusion proteins to analyze the subcellular localization of MK5. Although this protein is predominantly nuclear in unstimulated cells, MK5 shuttles between the nucleus and the cytoplasm. Furthermore, we have shown that the C-terminal domain of MK5 contains both a functional nuclear localization signal (NLS) and a leucine-rich nuclear export signal (NES), indicating that the subcellular distribution of this kinase reflects the relative activities of these two signals. In support of this, we have shown that stress-induced activation of the p38 MAPK stimulates the chromosomal region maintenance 1 protein-dependent nuclear export of MK5. This is regulated by both binding of p38 MAPK to MK5, which masks the functional NLS, and stress-induced phosphorylation of MK5 by p38 MAPK, which either activates or unmasks the NES. These properties may define the ability of MK5 to differentially phosphorylate both nuclear and cytoplasmic targets or alternatively reflect a mechanism whereby signals initiated by activation of MK5 in the nucleus may be transmitted to the cytoplasm.

3T3 Cells↗

A novel RNA species from the turtle mitochondrial genome: induction and regulation of transcription and processing under anoxic and freezing stresses.

The present study identifies a previously cloned cDNA, pBTaR914, as homologous to the mitochondrial WANCY (tryptophan, alanine, asparagine, cysteine, and tyrosine) tRNA gene cluster. This cDNA clone has a 304-bp sequence and its homologue, pBTaR09, has a 158-bp sequence with a long poly(A)+ tail (more than 60 adenosines). RNA blotting analysis using pBTaR914 probe against the total RNA from the tissues of adult and hatchling turtles revealed five bands: 540, 1800, 2200, 3200, and 3900 nucleotides (nt). The 540-nt transcript is considered to be an intact mtRNA unit from a novel mtDNA gene designated WANCYHP that overlaps the WANCY tRNA gene cluster region. This transcript was highly induced by both anoxic and freezing stresses in turtle heart. The other transcripts are considered to be the processed intermediates of mtRNA transcripts with WANCYHP sequence. All these transcripts were differentially regulated by anoxia and freezing in different organs. The data suggest that mtRNA processing is sensitive to regulation by external stresses, oxygen deprivation, and freezing. Furthermore, the fact that the WANCYHP transcript is highly induced during anoxic exposure suggests that it may play an important role in the regulation of mitochondrial activities to coordinate the physiological adaptation to anoxia.

Adaptation, Physiological↗

Thrombin, TNF-alpha, and LPS exert overlapping but nonidentical effects on gene expression in endothelial cells and vascular smooth muscle cells.

Thrombin, TNF-alpha, and LPS have each been implicated in endothelial cell and vascular smooth muscle cell (VSMC) activation. We wanted to test the hypothesis that these three agonists display mediator and/or cell type-specific properties. The addition of thrombin to human pulmonary artery endothelial cells resulted in an upregulation of PDGF-A, tissue factor (TF), ICAM-1, and urokinase-type plasminogen activator (u-PA), whereas TNF-alpha and LPS failed to induce PDGF-A. These effects were mimicked by protease-activated receptor-1 activation. In VSMC, thrombin induced expression of TF and PDGF-A but failed to consistently induce ICAM-1 or u-PA expression. In contrast, TNF-alpha and LPS increased expression of all four genes in this cell type. Inhibitor studies in endothelial cells demonstrated a critical role for PKC in mediating thrombin, TNF-alpha, and LPS induction of ICAM-1, TF, and u-PA and for p38 MAPK in mediating thrombin, TNF-alpha, and LPS induction of TF. Taken together, these results suggest that inflammatory mediators engage distinct signaling pathways and expression profiles in endothelial cells and VSMC. The data support the notion that endothelial cell activation is not an all-or-nothing phenomenon but rather is dependent on the nature of the extracellular mediator.

Cells, Cultured↗

Genome-wide analysis of mRNA lengths in Saccharomyces cerevisiae.

BACKGROUND: Although the protein-coding sequences in the Saccharomyces cerevisiae genome have been studied and annotated extensively, much less is known about the extent and characteristics of the untranslated regions of yeast mRNAs. RESULTS: We developed a 'Virtual Northern' method, using DNA microarrays for genome-wide systematic analysis of mRNA lengths. We used this method to measure mRNAs corresponding to 84% of the annotated open reading frames (ORFs) in the S. cerevisiae genome, with high precision and accuracy (measurement errors +/- 6-7%). We found a close linear relationship between mRNA lengths and the lengths of known or predicted translated sequences; mRNAs were typically around 300 nucleotides longer than the translated sequences. Analysis of genes deviating from that relationship identified ORFs with annotation errors, ORFs that appear not to be bona fide genes, and potentially novel genes. Interestingly, we found that systematic differences in the total length of the untranslated sequences in mRNAs were related to the functions of the encoded proteins. CONCLUSIONS: The Virtual Northern method provides a practical and efficient method for genome-scale analysis of transcript lengths. Approximately 12-15% of the yeast genome is represented in untranslated sequences of mRNAs. A systematic relationship between the lengths of the untranslated regions in yeast mRNAs and the functions of the proteins they encode may point to an important regulatory role for these sequences.

Blotting, Northern↗

Molecular portrait of the progestagenic and estrogenic actions of tibolone: behavior of cellular networks in response to tibolone.

Tibolone is a synthetic steroid with estrogenic effects on brain, vagina, and bone without stimulating the endometrium. During tibolone treatment, it is thought that the progestagenic properties of tibolone stimulate cell differentiation, which effectively counterbalances the growth-stimulating effects of the estrogenic properties of tibolone. The objective of this study was to characterize the expression profile that reflects the endometrial responses to the separated estrogenic (growth-inducing) and progestagenic (growth-inhibiting) actions of tibolone, thus gaining insight into the counteracting effect of these properties of tibolone on the endometrium. The estrogenic action of tibolone was studied in the estrogen-responsive ECC1 cell line (expressing estrogen receptor alpha), and the progestagenic action was studied in the progesterone-responsive cell line Ishikawa PRAB-36 (expressing PRA and PRB). The data showed that the progestagenic and estrogenic effects of tibolone produce different expression profiles with a narrow overlap in genes; however, both properties modulate the same biological processes. The final genetic network analysis indicated that the estrogenic effect of tibolone is potentially counterbalanced by the progestagenic metabolite of tibolone via differential regulation of similar cellular processes. For example, both progestagenic and estrogenic properties stimulate proliferation, but they exert the opposite effect on apoptosis. The apoptosis network was stimulated by the progestagenic properties of tibolone; in contrast, the estrogenic effect of tibolone suppressed the apoptosis network. The current results indicate that this differential regulation is realized through modulation of a different group of genes and rarely via contraregulation of the same set of genes.

Adenocarcinoma↗

Clinical review: Type 1 diabetes-associated autoimmunity: natural history, genetic associations, and screening.

CONTEXT: Type 1 diabetes (T1D) is associated with autoimmune thyroid disease (AIT), celiac disease (CD), Addison's disease (AD), and other autoimmune diseases. These diseases can occur together in defined syndromes with distinct pathophysiology and characteristics: autoimmune polyendocrine syndrome I, autoimmune polyendocrine syndrome II, and the immunodysregulation polyendocrinopathy enteropathy X-linked syndrome. EVIDENCE ACQUISITION: Review of the medical literature was performed with particular attention to the natural history, genetic factors, and syndromes associated with T1D, AIT, CD, and AD. EVIDENCE SYNTHESIS: Genetic risk for these diseases overlaps and includes genes within the major histocompatibility complex (MHC) such as the human leukocyte antigens (HLA) DR and DQ alleles and the MHC I-related gene A (MIC-A). Other genes outside of the MHC have been associated with these autoimmune diseases, including the gene encoding the lymphoid tyrosine phosphatase (PTPN22) and the cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) gene. CONCLUSION: Genetic risk for T1D overlaps with AIT, CD, and AD. Disease risk is associated with organ-specific autoantibodies, which can be used to screen subjects with T1D.

Adrenal Gland Diseases↗

The human sex hormone-binding globulin gene contains exons for androgen-binding protein and two other testicular messenger RNAs.

When a sex hormone-binding globulin (SHBG) cDNA was used to screen a human testicular cDNA library, three distinct cDNAs were isolated, one of which corresponds to the human SHBG cDNA sequence and probably represents testicular androgen-binding protein. The other two SHBG-related cDNAs each contain unique 5' regions that diverge from the SHBG cDNA sequence at the same position, and one of them (SHBGr-2) lacks a 208-base pair region within the SHBG cDNA. As a result, this cDNA could potentially encode for a truncated form of SHBG which lacks N-linked carbohydrates and part of the steroid-binding domain. Southern blots of human placental DNA and cloned genomic DNA fragments also indicate that SHBG and its related testicular cDNAs are the products of a single gene. Sequence analysis of the gene indicates that the complete coding region for the SHBG precursor is comprised of 8 exons, which are distributed over 3.2 kilobase (kb) of genomic DNA, and the unique 5' regions associated with the two SHBG-related testicular cDNAs were identified 1.9 kb upstream from the initiating codon for SHBG. In addition, the deletion within SHBGr-2 is due to the removal of exon 7, and an interesting feature of the gene is that differentially used exons are preceded by Alu repetitive DNA sequences. Although the relative abundance of the various SHBG-related mRNAs in the testis has not been established, Northern blot analysis indicates that they are similar in size (1.6 kb) to that of hepatic SHBG mRNA.

Amino Acid Sequence↗

A single gene encodes the beta-subunits of equine luteinizing hormone and chorionic gonadotropin.

Equine (e) CG and LH beta-subunits have identical amino acid sequences, including an extended carboxyl-terminal peptide (CTP). This suggests that unlike the corresponding human genes, the beta-subunits of eCG and eLH may be encoded by a single gene and share a common proximal promotor region. To explore this, we isolated and characterized the eLH/CG beta gene(s). Data from Southern analyses suggest that the eCG beta and eLH beta subunits are products of the same single copy gene (eLH/CG beta). Overlapping fragments of the eLH/CG beta gene and cDNA were amplified from equine genomic DNA and pituitary gland mRNA by the polymerase chain reaction, cloned, and sequenced. The eLH/CG beta gene spans less than 1.2 kilobase-pairs and has three exons that translate a CTP-containing polypeptide identical in sequence to that previously reported for the mature equine protein. There is, however, little amino acid homology shown between the CTP of human or equine CG beta subunit. In addition, unlike the human genes, the same TATAA-like element appears to be involved in directing initiation of transcription of the eLH/CG beta gene in placenta and anterior pituitary. Based upon these differences, we suggest that the CG beta genes evolved independently in humans and equids and that different mechanisms are involved in their patterns of placenta-specific expression.

Amino Acid Sequence↗

Genome-wide scan for Parkinson's disease: the GenePD Study.

A genome-wide scan for idiopathic PD in a sample of 113 PD-affected sibling pairs is reported. Suggestive evidence for linkage was found for chromosomes 1 (214 cM, lod = 1.20), 9 (136 cM, lod = 1.30), 10 (88 cM, lod = 1.07), and 16 (114 cM, lod = 0.93). The chromosome 9 region overlaps the genes for dopamine beta-hydroxylase and torsion dystonia. Although no strong evidence for linkage was found for any locus, these results may be of value in comparison with similar studies by others.

Aged↗

A Drosophila gene expressed in the embryonic CNS shares one conserved domain with the mammalian GAP-43.

By cross hybridization with the mammalian growth-related protein, GAP-43, we have isolated several Drosophila cDNAs and genomic sequences. These sequences correspond to a single copy gene that encodes two developmentally regulated transcripts 2.4 and 2.0 kb in length. The predicted protein sequence from the cDNAs contains a stretch of 20 amino acids closely related to the mammalian GAP-43 protein. These residues are also highly conserved in a cDNA isolated from the nematode C. elegans. Prior to dorsal closure, expression of the Drosophila gene is observed in non-neuronal tissues, especially in the mesectoderm and presumptive epidermis, both in a metameric pattern. After dorsal closure, expression becomes restricted to sets of cells that are segmentally reiterated along the periphery of the nervous system. These cells appear to include at least one specific set of glia that may establish scaffolding for the development of the longitudinal neuropile.

Amino Acid Sequence↗

The Drosophila Broad-Complex plays a key role in controlling ecdysone-regulated gene expression at the onset of metamorphosis.

During Drosophila third instar larval development, one or more pulses of the steroid hormone ecdysone activate three temporally distinct sets of genes in the salivary glands, represented by puffs in the polytene chromosomes. The intermolt genes are induced first, in mid-third instar larvae; these genes encode a protein glue used by the animal to adhere itself to a solid substrate for metamorphosis. The intermolt genes are repressed at puparium formation as a high titer ecdysone pulse directly induces a small set of early regulatory genes. The early genes both repress their own expression and activate more than 100 late secondary-response genes. The Broad-Complex (BR-C) is an early ecdysone-inducible gene that encodes a family of DNA binding proteins defined by at least three lethal complementation groups: br, rbp, and l(1)2Bc. We have found that the BR-C is critical for the appropriate regulation of all three classes of ecdysone-inducible genes. Both rbp and l(1)2Bc are required for glue gene induction in mid-third instar larvae. In addition, the l(1)2Bc function is required for glue gene repression in prepupae; in l(1)2Bc mutants the glue genes are re-induced by the late prepupal ecdysone pulse, recapitulating a mid-third instar regulatory response at an inappropriate stage in development. The l(1)2Bc function is also required for the complete ecdysone induction of some early mRNAs (E74A, E75A, and BR-C) and efficient repression of most early mRNAs in prepupae. Like the intermolt secondary-response genes, the late secondary-response genes are absolutely dependent on rbp for their induction. An effect of l(1)2Bc mutations on late gene activity can also be detected, but is most likely a secondary consequence of the submaximal ecdysone-induction of a subset of early regulatory products. Our results indicate that the BR-C plays a key role in dictating the stage-specificity of the ecdysone response. In addition, the ecdysone-receptor protein complex alone is not sufficient for appropriate induction of the early primary-response genes, but requires the prior expression of BR-C proteins. These studies define the BR-C as a key regulator of gene activity at the onset of metamorphosis in Drosophila.

Alleles↗

Clustered arrangement of winged helix genes fkh-6 and MFH-1: possible implications for mesoderm development.

The 'winged helix' or 'forkhead' transcription factor gene family is defined by a common 100 amino acid DNA binding domain which is a variant of the helix-turn-helix motif. Here we describe the structure and expression of the mouse fkh-6 and MFH-1 genes. Both genes are expressed in embryonic mesoderm from the headfold stage onward. Transcripts for both genes are localised mainly to mesenchymal tissues, fkh-6 mRNA is enriched in the mesenchyme of the gut, lung, tongue and head, whereas MFH-1 is expressed in somitic mesoderm, in the endocardium and blood vessels as well as the condensing mesenchyme of the bones and kidney and in head mesenchyme. Both genes are located within a 10 kb region (in mouse chromosome 8 at 5.26 +/- 2.56 cM telomeric to Actsk1. The close physical linkage of these two winged helix genes is conserved in man, where the two genes map to chromosome 16q22-24. This tandem arrangement suggests the common use of regulatory mechanisms. The fkh-6/MFH-1 locus maps close to the mouse mutation amputated, which is characterised by abnormal development of somitic and facial mesoderm. Based on the expression patterns we suggest that a mutation in MFH-1, not fkh-6 is the possible cause for the amputated phenotype.

Amino Acid Sequence↗

Tbx5 is essential for heart development.

Mutations in the Tbx5 transcription factor cause heart septal defects found in human Holt-Oram Syndrome. The complete extent to which Tbx5 functions in heart development, however, has not been established. Here we show that, in Xenopus embryos, Tbx5 is expressed in the early heart field, posterior to the cardiac homeobox transcription factor, Nkx2.5. During morphogenesis, Tbx5 is expressed throughout the heart tube except the anterior portion, the bulbus cordis. When Tbx5 activity is antagonized with a hormone-inducible, dominant negative version of the protein, the heart fails to develop. These results suggest that, in addition to its function in heart septation, Tbx5 has a more global role in cardiac specification and heart development in vertebrate embryos.

Amino Acid Sequence↗